Known undercarriages of hospital beds mostly have four or five wheels that can turn around their horizontal as well as vertical axis. The undercarriage has a control mechanism that comprises a common three-position control that can be controlled from several places, e.g. with a system of mechanically interconnected levers positioned at individual wheels.
In the central position of the levers of the three-position control all the wheels can freely turn around their horizontal as well as vertical axis. This position is referred to as “unbraked” in this application. The bed can be freely moved to all directions.
In the lower position of the levers of the three-position control turning of all the wheels both around the horizontal and around the vertical axis is blocked. This position is referred to as “braked” in this application. The movement of the bed is blocked.
Finally, in the upper position of the levers of the three-position control turning of one wheel around the vertical axis is locked in a pre-selected position, generally in the position that is parallel to the longitudinal axis of the bed. The other wheels can freely turn both around their horizontal and around their vertical axis. The bed can be moved while the wheel locked in the position parallel to the longitudinal axis of the bed facilitates keeping the straight movement direction for the personnel transporting patients along hospital corridors.
Known undercarriages of hospital beds with five wheels work in the same way while their fifth wheel is positioned under the centre of the bed and can be locked in a pre-selected position with the above mentioned three-position control, common for the control of the functions of all the wheels described above.
In the latest versions of undercarriages the control mechanism comprises a separate two-position control that controls brakes of all braked wheels and a separate control that controls locking of wheels the turning of which around the vertical axis can be locked in a pre-selected position.
A common disadvantage of all the known undercarriages for hospital beds is that if after stopping and putting the bed aside the staff member forgets to brake the undercarriage, the patient may get injured if he/she leans against the bed thinking that it is braked. In such a case the bed starts to move and the patient may fall, which may have severe consequences, especially in the case of older or disorientated patients.
So the aim of the invention is to design such an undercarriage for hospital beds that will exclude the above mentioned mistakes of the staff.